Field devices, for example traffic signal installations for traffic control, signal installations for trains, and switches, are usually connected to a control station or a signal box for the operating and monitoring thereof. In this context, the communication between field device and control station may take place both by wired connections (run cables) or also wirelessly by a radio link.
In order to be able to detect a physical manipulation at a field device by a possible attacker, sensors, for example motion sensors, may be used. In order to impede a manipulation of electronic circuits in the field device itself, hardware security-integrated circuits may be used that store cryptographic keys and perform cryptographic operations. Such integrated circuits usually have a tamper protection, for example in the form of sensors arranged directly on the integrated circuit. The sensors are designed for detecting an unauthorized opening of the integrated circuit.
Such a hardware security-integrated circuit may be a “trusted platform module,” the data for which can be found at http://en.wikipedia.org/wiki/Trusted_Platform_Module. For example, such integrated circuits are installed in PCs or notebooks.
The field of burglar alarm installations and alarm installations for buildings use contacts at doors and windows, and/or motion sensors for signaling a break-in or unauthorized opening or penetration into the building or into a room. In the case of a break-in into a building, for example, an alarm is triggered by a siren, or something similar, and it is also possible to contact a police operations center at the same time. To protect the alarm installation against manipulations, the sensors themselves may be equipped with so-called tamper sensors that detect a manipulation of the burglar alarm installation or of the alarm installation, especially when the housing is opened and/or a sensor is dismantled. The tamper sensors then transfer the information to the alarm installation that, in turn, triggers an alarm.
One way to protect parts of a circuit board or an entire circuit board against manipulation is to screw metal plates onto the circuit board in such a manner that a capacitor is formed overall. The capacitance of this capacitor is then continuously monitored so that in the case of a deviation of the normal capacitance value, for example by touching the metal plate or its removal, a change in the capacitance occurs. If a change in the capacitance is found, an alarm may be triggered and a memory on the board that, for example, contains sensitive data, may be deleted so that an attacker cannot obtain access to the sensitive data.